Use ATTRIBUTE_UNUSED more.

Use it in lieu of UNUSED(), which had some incorrect uses.

Change-Id: If247dce58b72056f6eea84968e7196f0b5bef4da
diff --git a/runtime/entrypoints/quick/quick_trampoline_entrypoints.cc b/runtime/entrypoints/quick/quick_trampoline_entrypoints.cc
index 377675e..6035dfe 100644
--- a/runtime/entrypoints/quick/quick_trampoline_entrypoints.cc
+++ b/runtime/entrypoints/quick/quick_trampoline_entrypoints.cc
@@ -1524,9 +1524,9 @@
     return sp8;
   }
 
-  virtual void WalkHeader(BuildNativeCallFrameStateMachine<ComputeNativeCallFrameSize>* sm)
+  virtual void WalkHeader(
+      BuildNativeCallFrameStateMachine<ComputeNativeCallFrameSize>* sm ATTRIBUTE_UNUSED)
       SHARED_REQUIRES(Locks::mutator_lock_) {
-    UNUSED(sm);
   }
 
   void Walk(const char* shorty, uint32_t shorty_len) SHARED_REQUIRES(Locks::mutator_lock_) {